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Measurement Mic Shootout (EMM-6, WM-61A, RS 33-2055, Audyssey) - Page 8

post #211 of 375
Quote:
Originally Posted by MKtheater View Post

Could you now add a correction file to the audyssey mic since you know how far off it is and then it too be a reference MIC? I am talking REW of course.


The Audyssey microphone seems to measure very well down to 15 Hz. Below that, do you really care about 100% accuracy?
post #212 of 375
Not dead accurate but enough to keep me in the ball park, say within 3 db's.
post #213 of 375
Thread Starter 
Quote:
Originally Posted by bossobass View Post


I will gladly send my AUD mic to notnyt, but I would like to know up front; if his results using my AUD mic are the same as his results using his AUD mic, then what would the conclusion be?

Bosso

I'll measure it up if you want to send it. Send me a PM if you want and I'll reply with my address.

If it measures the same, I have 4 different computers/laptops that I will retake the measurements with and then we can go from there. I do not expect it to measure the same. The RS 33-2050 measured low as expected. I'll post results from the other two RS meters in transit as soon as I receive them as well.

Quote:
Originally Posted by J_Palmer_Cass View Post

True as long as the FR of the reference microphone has not changed over time.

Maybe notnyt's reference microphone correction factors are off a bit?

I doubt this. Unless CSL is selling bunk calibrations which would mean his business is fraudulent, we can assume the EMM-6 correction tables I'm using are valid. I have the narrowband correction tables for 0, 45, and 90 degree orientations.
post #214 of 375
Quote:
Originally Posted by notnyt View Post

I doubt this. Unless CSL is selling bunk calibrations which would mean his business is fraudulent, we can assume the EMM-6 correction tables I'm using are valid. I have the narrowband correction tables for 0, 45, and 90 degree orientations.



Valid with what tolerance????????????????????????????????????????
post #215 of 375
Thread Starter 
Quote:
Originally Posted by J_Palmer_Cass View Post

Valid with what tolerance????????????????????????????????????????

How far off do you think it's going to be? We can always assume that there may be some tolerance required, but I don't believe it would be more than half a db. Generating a calibration against a reference mic isn't rocket science. This train of thought will not take you anywhere useful.
post #216 of 375
I guess the question remains then if you measure Bosso's Audyssey mic and get the same results as your Audyssey mic (it matches the measurements taken using the calibrated EMM-6) what is the conclusion?
post #217 of 375
Thread Starter 
Quote:
Originally Posted by lennon_68 View Post

I guess the question remains then what if you measure Bosso's Audyssey mic and get the same results as your Audyssey mic (it matches the measurements taken using the calibrated EMM-6)?

If it does, the only thing that I can assume is there is some odd mic preamp issues on a soundcard somewhere. If it does match, I will test this with all the computers I have, which are all compromised of different hardware to rule out fault on this side. If I can't find any fault, I'll go ahead and send my EMM-6 out to be compared to Bosso's ACOPacific if he wants..

Keep in mind, I have been able to recreate my results using one of my laptops.
post #218 of 375
Quote:
Originally Posted by notnyt View Post

Unless CSL is selling bunk calibrations which would mean his business is fraudulent,
.

Which would result in the loss of my PE license and would allow several lawyers to have a field day with expert witness testimony I've given. Not good times
post #219 of 375
Thread Starter 
Quote:
Originally Posted by Anechoic View Post

Which would result in the loss of my PE license and would allow several lawyers to have a field day with expert witness testimony I've given. Not good times

Hence why I ruled that out as an option fairly quickly
post #220 of 375
Quote:
Originally Posted by notnyt View Post

How far off do you think it's going to be? We can always assume that there may be some tolerance required, but I don't believe it would be more than half a db. Generating a calibration against a reference mic isn't rocket science. This train of thought will not take you anywhere useful.



I don't care what you believe. What can you prove?

Here is a list of Aco Pacific microphones. What do you believe the tolerance should be, better than plus or minus 1/2 dB?


http://www.libinst.com/aco_pacific_microphones.htm



Quote:
Originally Posted by notnyt View Post

This train of thought will not take you anywhere useful.


Everything and everyone being considered, you are correct!
post #221 of 375
Thread Starter 
Quote:
Originally Posted by J_Palmer_Cass View Post

I don't care what you believe. What can you prove?

Here is a list of Aco Pacific microphones. What do you believe the tolerance should be, better than plus or minus 1/2 dB?


http://www.libinst.com/aco_pacific_microphones.htm






Everything and everyone being considered, you are correct!

Well, Anechoic/Herb calibrated this EMM-6, he can chime in with how close his calibrations are if he chooses. Judging by the resolution used and the procedure, I don't assume it would be very far off.

At this point it seems like you're blindly pointing fingers.
post #222 of 375
Quote:
Originally Posted by notnyt View Post

Well, Anechoic/Herb calibrated this EMM-6, he can chime in with how close his calibrations are if he chooses. Judging by the resolution used and the procedure, I don't assume it would be very far off.

My cals (probably) are not +/- 0.5 dB accurate, certainly not across the full bandwidth of the measurement. If we start with the reference mic (which I get regularly calibrated by Scantek, an NVLAP/NIST-traceable lab), their cal methods have an uncertainly of 0.2 dB from 200-8000 Hz, 0.6 dB from 8-10 kHz and 0.9 dB from 10-20 kHz using an electrostatic actuator.

I haven't done a complete statistical analysis of the accuracy and precision of my method, but I've compared results I get with my setup with the results Scantek has generated for my other ANSI-rated mics to get an idea of the accuracy.

I use a free-field substitution method for the data about 100 Hz. The results about about 8 kHz is extremely sensitive to mic placement and room effects which cause most of the error. Below 100 Hz I use the substitution method in a pressure chamber and the error comes from imperfect seals around the mic capsule in the coupler (this is an issue with the EMM-6 and ECM8000 since they are slightly smaller in diameter than my 1/2 ACO 7052, so I have to pad out the diameter with electrical tape to get a good fit in the coupler).

Given the above, the data I provide from 100 Hz to around 3-5 kHz is accurate to around +/- 1 to 1.5 dB. Below 100 Hz and above 8 kHz or so the error increases, probably in the neighborhood of +/- 2-3 dB (perhaps more in the highest or lowest octave). The substitution method in principle is relatively simple but in practice there is a lot that can cause error. I think this is one of the reasons why NIST-traceable labs don't bother with this method (they all use electrostatic actuators now).

(in another thread either here, on hometheatershack.com htguide.com, or parts-express.com I have some accuracy numbers that were based on some quick calcs I did on data, and this post is an attempt to remember those numbers. If there is any conflict between this post and the earlier post, go with the numbers in the other post).

I do know that my method is repeatable. Every once in a while, I have an overseas delivery go awry and I get a microphone returned to me after it's been sitting in a foreign post office for a month or so. When I test it again, the result is always within +/- 0.5 dB of what I got previously. Thank heaven for small favors.
post #223 of 375
Quote:
Originally Posted by Anechoic View Post

My cals (probably) are not +/- 0.5 dB accurate, certainly not across the full bandwidth of the measurement. If we start with the reference mic (which I get regularly calibrated by Scantek, an NVLAP/NIST-traceable lab), their cal methods have an uncertainly of 0.2 dB from 200-8000 Hz, 0.6 dB from 8-10 kHz and 0.9 dB from 10-20 kHz using an electrostatic actuator.

I haven't done a complete statistical analysis of the accuracy and precision of my method, but I've compared results I get with my setup with the results Scantek has generated for my other ANSI-rated mics to get an idea of the accuracy.

I use a free-field substitution method for the data about 100 Hz. The results about about 8 kHz is extremely sensitive to mic placement and room effects which cause most of the error. Below 100 Hz I use the substitution method in a pressure chamber and the error comes from imperfect seals around the mic capsule in the coupler (this is an issue with the EMM-6 and ECM8000 since they are slightly smaller in diameter than my 1/2 ACO 7052, so I have to pad out the diameter with electrical tape to get a good fit in the coupler).

Given the above, the data I provide from 100 Hz to around 3-5 kHz is accurate to around +/- 1 to 1.5 dB. Below 100 Hz and above 8 kHz or so the error increases, probably in the neighborhood of +/- 2-3 dB (perhaps more in the highest or lowest octave). The substitution method in principle is relatively simple but in practice there is a lot that can cause error. I think this is one of the reasons why NIST-traceable labs don't bother with this method (they all use electrostatic actuators now).

(in another thread either here, on hometheatershack.com htguide.com, or parts-express.com I have some accuracy numbers that were based on some quick calcs I did on data, and this post is an attempt to remember those numbers. If there is any conflict between this post and the earlier post, go with the numbers in the other post).

I do know that my method is repeatable. Every once in a while, I have an overseas delivery go awry and I get a microphone returned to me after it's been sitting in a foreign post office for a month or so. When I test it again, the result is always within +/- 0.5 dB of what I got previously. Thank heaven for small favors.



The problem area being discussed is the sub 20 Hz area. The above talks about everything except this low frequency area. No disagreement on measurements of frequencies above 20 Hz.


The bottom line is notnyt measured an Audyssey microphone with no factors being applied, and it compares well with the calibrated EMM-6 with factors being applied. If those measurements are correct, then that means the Audyssey microphone measures almost the same as your reference microphone below 20 Hz.


One would expect some rolloff starting at about 20 Hz with any of the basic microphones that use an inexpensive element. Funny how both you and Bosso both show an Audyssey microphone measures about 4 dB low @ 10 Hz with the various Audyssey microphones being compared with a nice reference microphone.

I note that your calibration tolerance is +/- 2 to 3 dB ("or perhaps more") at the extreme low and high end. That's all I needed to know to put this to bed!






post #224 of 375
Quote:
Originally Posted by notnyt View Post

Well, Anechoic/Herb calibrated this EMM-6, he can chime in with how close his calibrations are if he chooses. Judging by the resolution used and the procedure, I don't assume it would be very far off.

At this point it seems like you're blindly pointing fingers.



Herb gave you the answer. Hardly you assumed +/- 1/2 dB in the frequency area of interest!


"Below 100 Hz and above 8 kHz or so the error increases, probably in the neighborhood of +/- 2-3 dB (perhaps more in the highest or lowest octave)."
post #225 of 375
Thread Starter 
If you were following along, those are different Audyssey microphones. Herb measured the pro mics, Bosso measured the mics that come with receivers.
post #226 of 375
Thread Starter 
I just received MKTheaters mic. I'm going to test that in a minute.
post #227 of 375
Quote:
Originally Posted by notnyt View Post

If you were following along, those are different Audyssey microphones. Herb measured the pro mics, Bosso measured the mics that come with receivers.



If you were following along, Herb gave you the answer to calibration tolerances. Hardly your assumed +/- 1/2 dB in the frequency area of interest!


"Below 100 Hz and above 8 kHz or so the error increases, probably in the neighborhood of +/- 2-3 dB (perhaps more in the highest or lowest octave)."
post #228 of 375
Thread Starter 
I saw them, however you're assuming the worst case scenario.

The bottom line that I'm seeing right now, is that all of these mics have measured within 1db of each other down to 10hz.

Are you saying that all of these mics are equally wrong, including capsules known to measure accurate to single digit frequencies and a calibrated EMM-6?

Here are the results with MKTheaters meter.



Here is down to 5hz. His RS meter begins deviations at the same point as my RS meter.



Here is a full range graph comparing two RS meters and the EMM-6
post #229 of 375
Thread Starter 
Here is the internals of my RS meter. It has a WD capsule. Judging by the markings, this design hasn't changed.

post #230 of 375
Well it looks like I will have to remeasure my subs with just c-weighted and not cal files. I have done this before and my subs were 8 db's down at 10hz.
post #231 of 375
Thread Starter 
Quote:
Originally Posted by MKtheater View Post

Well it looks like I will have to remeasure my subs with just c-weighted and not cal files. I have done this before and my subs were 8 db's down at 10hz.

Unless someone has another explanation for why all of these mic's would measure similarly low.

J Palmer seems to think the calibration of the EMM-6 is off, but that doesn't explain why the rest of the capsules measure within a decibel to the calibrated curve.

Also just FYI, in REW 5 at least, you don't have to re-measure. You can change the calibration on saved graphs very easily.
post #232 of 375
Quote:
Originally Posted by notnyt View Post

Unless someone has another explanation for why all of these mic's would measure similarly low.

J Palmer seems to think the calibration of the EMM-6 is off, but that doesn't explain why the rest of the capsules measure within a decibel to the calibrated curve.

Also just FYI, in REW 5 at least, you don't have to re-measure. You can change the calibration on saved graphs very easily.

Yeah, but this means all my graphs were off so now I have no comparison of any sub systems. The first real graph will be of my CS subs and my next DIY project. I think what the guys are trying to say that how can $40 meters be as accurate as pro calibrated mics? No one would ever buy the better mics. I just bought the lilmike mic and will use that for now on.
post #233 of 375
Thread Starter 
Just in case anyone is interested, here is the Dayton vs CSL calibrations for my EMM-6 mic.



Also, I downloaded all of Dayton's EMM-6 calibration files and graphed a bunch of them.
I see why their paper printout only goes down to 25hz. It looks like their measurement rig goes off below there.



It also looks like there was a change made to the EMM-6 at some point. This is what the earlier calibrations look like. They drop off below 30hz and above 10khz.

post #234 of 375
Quote:
Originally Posted by notnyt View Post

It also looks like there was a change made to the EMM-6 at some point.

There was a change. The barrel is about a millimeter thinner now, and all the ones I've seen in the last few months show that rising response above 10 kHz. I haven't taken one of the newer ones apart to see if anything internal has changed. If I get chance, I'll run an output impedance test, that should give some indication about internal changes.
post #235 of 375
Thread Starter 
Quote:
Originally Posted by Anechoic View Post
There was a change. The barrel is about a millimeter thinner now, and all the ones I've seen in the last few months show that rising response above 10 kHz. I haven't taken one of the newer ones apart to see if anything internal has changed. If I get chance, I'll run an output impedance test, that should give some indication about internal changes.
So what's your take on the measurements that I've performed?

I have the EMM-6(CSL calibration), two Linkwitz modified WM-61A's(no cal), an Audyssey mic(no cal), and two RS meters(c weighed compensation) all measuring within 1db of each other from 7-200hz. I also have an older RS meter measuring lower as expected
post #236 of 375
Quote:
Originally Posted by notnyt View Post
So what's your take on the measurements that I've performed?

I have the EMM-6(CSL calibration), two Linkwitz modified WM-61A's(no cal), an Audyssey mic(no cal), and two RS meters(c weighed compensation) all measuring within 1db of each other from 7-200hz. I also have an older RS meter measuring lower as expected
It's not a result I would have expected, particularly with the Rat Shack meters which have had low-frequency results all over the place when I've measured them. But at first glance, the methodology seems sound.
post #237 of 375
Thread Starter 
Quote:
Originally Posted by Anechoic View Post
It's not a result I would have expected, particularly with the Rat Shack meters which have had low-frequency results all over the place when I've measured them. But at first glance, the methodology seems sound.
Same here, but I can't find any abnormal explanations.

Anyway, here's the graph plotted with the old RS meter with C weighted compensation in there as well for comparison.

post #238 of 375
Quote:
Originally Posted by notnyt View Post

Here is a full range graph comparing two RS meters and the EMM-6




Did you do anything different when you made that chart? The low bass is much higher than what can be seen in previous charts.

Why don't you do a couple of full range charts of a full range speaker? Above 100 Hz is all that is needed.




A couple of full range charts taken with the RS 30-2055 Digital SPL meter. The meter is useless above 10 kHz.

The RS 30-2055 Digital SPL meter measures flat when held at 90 degrees. There is a broad peak in the 7-8 kHz area if you point the meter at the sound source.





post #239 of 375
Thread Starter 
Quote:
Originally Posted by J_Palmer_Cass View Post

Did you do anything different when you made that chart? The low bass is much higher than what can be seen in previous charts.

Why don't you do a couple of full range charts of a full range speaker? Above 100 Hz is all that is needed.




A couple of full range charts taken with the RS 30-2055 Digital SPL meter. The meter is useless above 10 kHz.

The RS 30-2055 Digital SPL meter measures flat when held at 90 degrees. There is a broad peak in the 7-8 kHz area if you point the meter at the sound source.


The bass is higher in the full range graph you are asking about because I didn't feel like taking the time to adjust the levels of my subs. They were boosted a lot because I was listening to some music that way. It's not really relevant since I took a new sweep with the EMM-6 then both RS 33-2055s. I would never be able to find the exact position of the first measurements, so to compare both 33-2055's I had to take new ones.

I forgot to measure full range with the 33-2050 when it was here, I'll have to do that again. However, if you look in the first post, I have full range graphs posted for the newer meter. Here is one with the RS 33-2055 and the EMM-6. The RS meter's were pointed at the ceiling for the graph you quoted and the one below.

post #240 of 375
Just for the halibut: Do you have an older version of REW to compare to V5?

Bosso
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